In the deadliest attack inside Russia in 20 years, gunmen opened fire with automatic weapons at concertgoers on March 22 at the Crocus City Hall, killing at least 144 people in violence claimed by the Islamic State terrorist group.
"Days before the attack in Russia, Tehran shared information with Moscow about a possible big terrorist attack inside Russia that was acquired during interrogations of those arrested in connection with deadly bombings in Iran," said one source.
Iran's intelligence ministry said in January it had arrested 35 people linked to twin bombings on Jan. 3 in the southeastern city of Kerman that killed nearly 100 people. On Jan. 19, the ministry said it had arrested a commander of Islamic State's Afghanistan-based branch ISIS-Khorasan (ISIS-K).
Islamic State claimed responsibility for the Iran blasts, the bloodiest since the 1979 Islamic Revolution. US intelligence sources said ISIS-K had carried out both the Jan. 3 attacks in Iran and the March 22 shootings in Moscow. READ MORE
